On 13 Apr 2004 at 19:36, Simon Chamaill� wrote: You could maybe try gls in package nlme, where you can estimate parameters in variance functions. If you need a generalized linear model, you could have a look at glmmPQL in MASS, but I don't know if that accepts models without random effects.
Kjetil Halvorsen > Hello all, > I'm running very simple regression but face a problem of > non-homogeneity of variance, but with a decreasing variance with > increasing mean...I do not know how to deal with that. this > relationship doesn't seem to be strong, but it's my first time to see > something like that, and would like to know what to do if one day it > becomes stronger. I tested just for fun some transformation but was > not able to get a better model. I do not know if it can help, but my > predictor variable is a kind of gamma poisson-shaped-like zero-rich > distribution (continuous of course), highly overdispersed. If one know > how to deal with decreasing variance, I would appreciate any advice (I > tried to modelize negative variance-mean relationship in a new quasi- > family this was prohibited, only constant, mu, mu^x (and mu(1-mu) for > binomial) were allowed). I've definitively reached the border of the > statistical black box for me. thanks simon > > [[alternative HTML version deleted]] > > ______________________________________________ > [EMAIL PROTECTED] mailing list > https://www.stat.math.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide! > http://www.R-project.org/posting-guide.html ______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
